/*
 * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef AZEROTHCORE_CRYPTOHASH_H
#define AZEROTHCORE_CRYPTOHASH_H

#include "CryptoConstants.h"
#include "Errors.h"
#include <array>
#include <openssl/evp.h>
#include <string>
#include <string_view>
#include <utility>

class BigNumber;

namespace Acore::Impl
{
    struct GenericHashImpl
    {
        typedef EVP_MD const* (*HashCreator)();

        static EVP_MD_CTX* MakeCTX() noexcept { return EVP_MD_CTX_new(); }
        static void DestroyCTX(EVP_MD_CTX* ctx) { EVP_MD_CTX_free(ctx); }
    };

    template <GenericHashImpl::HashCreator HashCreator, std::size_t DigestLength>
    class GenericHash
    {
        public:
            static constexpr std::size_t DIGEST_LENGTH = DigestLength;
            using Digest = std::array<uint8, DIGEST_LENGTH>;

            static Digest GetDigestOf(uint8 const* data, std::size_t len)
            {
                GenericHash hash;
                hash.UpdateData(data, len);
                hash.Finalize();
                return hash.GetDigest();
            }

            template <typename... Ts>
            static auto GetDigestOf(Ts&&... pack) -> std::enable_if_t<!(std::is_integral_v<std::decay_t<Ts>> || ...), Digest>
            {
                GenericHash hash;
                (hash.UpdateData(std::forward<Ts>(pack)), ...);
                hash.Finalize();
                return hash.GetDigest();
            }

            GenericHash() : _ctx(GenericHashImpl::MakeCTX())
            {
                int result = EVP_DigestInit_ex(_ctx, HashCreator(), nullptr);
                ASSERT(result == 1);
            }

            GenericHash(GenericHash const& right) : _ctx(GenericHashImpl::MakeCTX())
            {
                *this = right;
            }

            GenericHash(GenericHash&& right) noexcept
            {
                *this = std::move(right);
            }

            ~GenericHash()
            {
                if (!_ctx)
                    return;
                GenericHashImpl::DestroyCTX(_ctx);
                _ctx = nullptr;
            }

            GenericHash& operator=(GenericHash const& right)
            {
                if (this == &right)
                    return *this;

                int result = EVP_MD_CTX_copy_ex(_ctx, right._ctx);
                ASSERT(result == 1);
                _digest = right._digest;
                return *this;
            }

            GenericHash& operator=(GenericHash&& right) noexcept
            {
                if (this == &right)
                    return *this;

                _ctx = std::exchange(right._ctx, GenericHashImpl::MakeCTX());
                _digest = std::exchange(right._digest, Digest{});
                return *this;
            }

            void UpdateData(uint8 const* data, std::size_t len)
            {
                int result = EVP_DigestUpdate(_ctx, data, len);
                ASSERT(result == 1);
            }

            void UpdateData(std::string_view str) { UpdateData(reinterpret_cast<uint8 const*>(str.data()), str.size()); }
            void UpdateData(std::string const& str) { UpdateData(std::string_view(str)); } /* explicit overload to avoid using the container template */
            void UpdateData(char const* str) { UpdateData(std::string_view(str)); } /* explicit overload to avoid using the container template */

            template <typename Container>
            void UpdateData(Container const& c) { UpdateData(std::data(c), std::size(c)); }

            void Finalize()
            {
                uint32 length;
                int result = EVP_DigestFinal_ex(_ctx, _digest.data(), &length);
                ASSERT(result == 1);
                ASSERT(length == DIGEST_LENGTH);
            }

            Digest const& GetDigest() const { return _digest; }

        private:
            EVP_MD_CTX* _ctx{};
            Digest _digest{};
    };
}

namespace Acore::Crypto
{
    using MD5 = Acore::Impl::GenericHash<EVP_md5, Constants::MD5_DIGEST_LENGTH_BYTES>;
    using SHA1 = Acore::Impl::GenericHash<EVP_sha1, Constants::SHA1_DIGEST_LENGTH_BYTES>;
    using SHA256 = Acore::Impl::GenericHash<EVP_sha256, Constants::SHA256_DIGEST_LENGTH_BYTES>;
}

#endif
